Study on the Arc Quenching Process in Gas Circuit Breakers

Abstract

A computational approach was developed to analyze the arc quenching process in the GCB. This approach, which takes into account all spaces related to the arc quenching, is capable of calculating the thermodynamic quantities of the gas as a function of time. Based on the so-called FLIC method, this program adopts a modification of the 'Simplified Enthalpy Arc Model'. Moreover, to assure the effectiveness of our program, the entire arc quenching process, which is based on the self-flow generation phenomena/current interruption, was reproduced using a thermal expansion type circuit breaker. This program, which was verified through experiments, produced good results. IntroductionThe nozzle clogging by the arc in the high current area when the arc quenching process in the GCB (Gas Circuit Breaker) begins has generally been regarded as being disadvantageous. However, some reports have indicated that, as the arc's blocking of the entrance of the nozzle results in an increase in the pressure of the arc chamber, the interrupting capability at current zero is in fact increased.[1] This development reinforces arguments that the effect caused by the blocking of the nozzle should be included in any theoretical analysis of the arc quenching phenomenon. Despite this, it has so far proven difficult to include changes in the arc radius and the effects of the blocking of the nozzle during the arc quenching process in a heat analysis. This paper has developed a program based on a computational approach that is designed to analyze the arc quenching process occurring within the arc contact system of the GCB. By calculating the thermodynamic quantities of plasma gas between the cold gas and plasma arc generated by the interrupting current, this analysis program proved itself capable of calculating the whole self-flow generation process in the GCB, including the arc. To analyze the arc in the GCB, this program, which is based on the FLIC (Fluid in Cell) method[2], applied an arc heat analysis that was based on a modified version of the simplified enthalpy arc model. To assure the accuracy of the arc heat analysis, and to obtain reliable results for the thermodynamic quantities generated by the arc plasma, this paper selected an SF6 thermal-expansion type gas circuit breaker (hereafter referred to as a GCB); which unlike the puffer method does not have a motion sensor in the contact system; as the model for the experiments. The FLIC method was used for the gas-flow analysis in order to analyze the